How does radon gas enter buildings?

Radon gas can enter a building from the ground, mainly by rising through cracks, service penetrations and cavities. In some cases, building materials may also release radon, although generally to a lesser extent than radon originating from the soil. Ventilating indoor spaces is essential to help reduce indoor radon concentrations.

Radon gas enters buildings mainly from the ground. As a naturally occurring radioactive gas produced by the decay of uranium found in rocks and soil, radon tends to rise towards the surface and may infiltrate enclosed spaces.

The main entry routes are:

• Cracks in floors and walls – Cracks in a building’s foundations and walls can allow radon to enter indoor spaces easily.
• Construction joints – Junctions between walls and floors, or between different building materials, may act as entry points.
• Openings for pipes and cables – Penetrations created for plumbing, electrical and ventilation systems can facilitate radon ingress.
• Underground wells and cavities – Cellars, crawl spaces and basement rooms in contact with the ground are particularly vulnerable.
• Building materials – Certain materials, such as tuff and granite, may contain uranium and release radon inside the building.
• Water – Water from underground sources or wells may contain radon, which is released into the air when the water is used, for example during showering or cooking.

Radon gas accumulates mainly in enclosed and poorly ventilated spaces, particularly on lower floors and in basements.

Mechanical ventilation with heat recovery – MVHR – is one of the most effective strategies for mitigating radon in buildings, provided that the system is correctly sized by professionals experienced in radon remediation. It helps reduce indoor radon concentrations through continuous and controlled air renewal.